This invention relates to electric power generating stations, and more particularly to a deeply submersible, and surfacable, condensing containment system for a nuclear powered electricity generator.
For the past three decades proposals were developed for siting nuclear power plants offshore to take advantage of the virtually limitless supply of cooling seawater and available seafloor real estate. These sites also satisfied the goal of removing power plants from population centers, yet could be closer to urban areas than could be achieved by siting in rural land areas.
One such proposal developed by Electric Boat was a slipway launched submarine plant to be emplaced on the seabed in 250 feet of water. It would have been manned through an access trunk from a platform above the sea's surface. Studies by Electric Boat showed the concept to be technically feasible and economically competitive with plants of similar size on land. A vessel colliding with the ever present trunk would have flooded this access and isolated the plant.
Offshore Power Systems, a joint venture between Westinghouse and Newport News Shipbuilding, developed, but did not build a barge mounted nuclear powerplant for shipyard construction and subsequent mooring within a cofferdam. Construction of this cofferdam would have required substantial dredging of the continental shelf and was widely opposed by local, environmental, fishing and shipping interests.
In the early 1980's, U.S. Pat. No. 4,302,291 was issued for an underwater nuclear power plant structure of three joined 150 foot spheres permanently moored by means of flexible cable several hundred feet beneath the surface. It was to be stabilized by an inverted, ballasted kingpost and backup dynamic positioning equipment. An alternative siting method was a pile foundation, stabilized by an automatic ballast and trim system. The spheres inner shell is two inch steel, overlaid by a 6½ foot thick shell of ferroconcrete. A personnel airlock/decompression chamber (136) serves for access and resupply by submersible service vessels. In an emergency, this chamber can be detached for a free ascent, by means of explosive bolts. In the event of a loss of coolant accident (LOCA) or steamline break, the increase in pressure opens doors to allow steam to rise through ice baskets (156) condensing the steam.
More recently, U.S. Pat. No. 5,247,553 was issued covering a “Submerged Passively-Safe Power Plant” that uses seawater to cool the reactor compartment in an emergency: seawater, guided between a double hull, would cool the 100 mm/4″ thick, 1634 square meter inner hull, and the reactor within. A suddenly isolated 600 MWe reactor at full power would produce over 1800 MWt, an incredible cooling load in excess of one million watts for each square meter of the inner hull. Peak temperatures in the fuel rods under such conditions would be disastrous.
Thus the limitations apparent in the prior proposals require further evolution if these offshore sites are to be utilized. To gain acceptance and succeed economically, a submerged generating application must greatly improve personnel safety and accessibility, and also decrease complexity and environmental impact over the prior proposals. The present invention is unmanned, surfacable, compact, and unintrusive.